Citrobacter freundii

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Scientific classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Citrobacter
Species: C. freundii

Citrobacter freundii is a species of facultative, anaerobic Gram-negative bacilli of the Enterobacteriaceae family.[1] The bacteria are long bacterial rods with a typical length of 1–5 μm.[2] Most C. freundii cells generally have several flagella used for locomotion, but some do not and are non-motile. C. freundii is a soil organism, but can also be found in water, sewage, food and in the intestinal tracts of animals and humans.[2] The Citrobacter genus was discovered in 1932 by Werkman and Gillen. Cultures of C. freundii were isolated and identified in the same year from soil extracts.[2]

As an opportunistic pathogen, C. freundii is responsible for a number of significant infections. It is known to be the cause of nosocomial infections of the respiratory tract, urinary tract, blood, and many other normally sterile sites in patients.[3] C. freundii represents about 29% of all opportunistic infections.[3]

Though a pathogen to humans, this infectious microbe in humans plays a an important role in the nitrogen cycle in the environment. C. freundii is responsible for reducing nitrate to nitrite in the environment.[4] This conversion is an important and crucial stage in the nitrogen cycle.

C. freundii has also been investigated for biodegradation of tannic acid used in tanneries.[4]

C. freundii has the ability to grow on glycerol, and use it as its sole source of carbon and energy. The organism contains a bacterial microcompartment which is capable of processing propanediol.[5]


  1. ^ "Citrobacter SPP.". Pathogen Safety Data Sheet — Infectious Substances. Public Health Agency of Canada. 2012. 
  2. ^ a b c Wang, J. T.; Chang, S. C.; Chen, Y. C.; Luh, K. T. (2000). "Comparison of antimicrobial susceptibility of Citrobacter freundii isolates in two different time periods". Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi 33 (4): 258–262. PMID 11269372. 
  3. ^ a b Whalen, J. G.; Mully, T. W.; English, J. C. (2007). "Spontaneous Citrobacter freundii Infection in an Immunocompetent Patient". Archives of Dermatology 143 (1): 124–125. doi:10.1001/archderm.143.1.124. PMID 17224563. 
  4. ^ a b Puchenkova, S. G. (1996). "Enterobacteria in areas of water along the Crimean coast". Mikrobiolohichnyi zhurnal (Kiev, Ukraine : 1993) 58 (2): 3–7. PMID 8983520. 
  5. ^ Pang, A.; Warren, M. J.; Pickersgill, R. W. (2011). "Structure of PduT, a trimeric bacterial microcompartment protein with a 4Fe–4S cluster-binding site". Acta Crystallographica Section D Biological Crystallography 67 (2): 91–96. doi:10.1107/S0907444910050201. PMID 21245529. 

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